1. Field of the Invention
The present invention relates to an optical module, an optical add/drop apparatus, and an optical transmission apparatus which are used in optical communications and the like.
2. Related Background Art
Known as an example of optical modules employed in optical communications and the like is the WDM DROP module described in IEEE Photonics Technology Letters, Vol. 11, No. 1, January 1999. This module has a configuration in which optical components such as an optical switch and an optical variable attenuator are connected to each other with an optical fiber and contained in a housing.
In the above-mentioned prior art, however, the optical components such as an optical switch and an optical variable attenuator are prepared separately from each other, whereby it takes time and labor to make these optical components, and the manufacturing cost becomes higher.
It is an object of the present invention to provide an optical module, an optical add/drop apparatus, and an optical transmission apparatus which can be manufactured easily at a low cost.
In one aspect, the present invention provides an optical module comprising at least one optical switch and at least one optical variable attenuator; the optical module further comprising a planar optical waveguide having a first optical circuit constituting a part of the optical switch and a second optical circuit constituting a part of the optical variable attenuator; and an actuator structure, connected to the planar optical waveguide, having a first actuator section constituting a part of the optical switch and a second actuator section constituting a part of the optical variable attenuator.
In this aspect of the present invention, the first optical circuit of the planar waveguide and the first actuator section of the actuator structure constitute an optical switch, whereas the second optical circuit of the planar waveguide and the second actuator section of the actuator structure constitute an optical variable attenuator. Since the first and second optical circuits are thus integrated in one planar waveguide, a part of the optical switch and a part of the optical variable attenuator are prepared collectively, whereby the optical switch and optical variable attenuator can be made easily at a low cost. Also, when such a planar waveguide having first and second optical circuits is used, it is unnecessary for the optical switch and optical variable attenuator to be connected to each other with an optical fiber when they are needed to be connected together. This can make the optical module smaller, while reducing the splice loss.
Preferably, the first optical circuit has an optical waveguide formed like a cross across a groove provided in the planar waveguide; whereas the first actuator section comprises a movable mirror for reflecting light passing through the optical waveguide, and driving means for moving the movable mirror, the movable mirror being disposed so as to be inserted into the groove. When the movable mirror is located at a predetermined position, for example, the light passing through one optical waveguide is reflected by the movable mirror so as to be guided to another optical waveguide located on the same side of the groove. If the movable mirror is moved by the driving means from this state, the light passing through one optical waveguide will pass through the groove, so as to be guided to another optical waveguide located on the opposite side of the groove. Thus, an optical switch constituted by the first optical switch and first actuator section can be realized with a simple configuration.
Preferably, the second optical circuit has an optical waveguide formed like a cross across a groove provided in the planar waveguide; whereas the second actuator section comprises a movable mirror for reflecting light passing through the optical waveguide, and driving means for moving the movable mirror, the movable mirror being disposed so as to be inserted into the groove. When the movable mirror is located at a predetermined position, for example, the light passing through one optical waveguide is totally reflected by the movable mirror so as to be guided to another optical waveguide located on the same side of the groove, whereby the amount of optical attenuation is minimized. If the movable mirror is moved by the driving means from this state, only a part of the light passing through the optical waveguide will be reflected by the movable mirror, whereby the amount of optical attenuation will increase. Thus, an optical variable attenuator constituted by the second optical switch and second actuator section can be realized with a simple configuration utilizing the reflection of light effected by the movable mirror.
Preferably, in the above-mentioned case, the movable mirror is attached to a cantilever supported on the planar waveguide; whereas the driving means comprises an electrode disposed on the planar waveguide, and means for generating an electrostatic force between the cantilever and the electrode. When an electrostatic force is utilized for driving the movable mirror as such, no current flow is necessary, whereby the power consumption can be reduced.
Preferably, a plurality of optical switches and a plurality of optical variable attenuators, each having a width of 500 xcexcm or less, are arranged in arrays. As a consequence, an optical module having a plurality of optical switches and a plurality of optical variable attenuators can be made smaller and highly integrated.
In another aspect, the present invention provides an optical module comprising at least one optical switch and at least one optical coupler; the optical module further comprising a planar optical waveguide having a first optical circuit constituting a part of the optical switch and a second optical circuit constituting the optical coupler; and an actuator structure, connected to the planar optical waveguide, constituting a part of the optical switch.
In this aspect of the present invention, the first optical circuit of the planar waveguide and the actuator structure constitute an optical switch, whereas the second optical circuit of the planar waveguide constitutes an optical coupler. Since the first and second optical circuits are thus integrated in one planar waveguide, a part of the optical switch and the optical coupler are prepared together, whereby the optical switch and optical coupler can be made easily at a low cost. Also, when such a planar waveguide having first and second optical circuits is used, it is unnecessary for the optical switch and optical coupler to be connected to each other with an optical fiber when they are needed to be connected together. This can make the optical module smaller, while reducing the splice loss.
Preferably, the first optical circuit has an optical waveguide formed like a cross across a groove provided in the planar waveguide; whereas the actuator structure comprises a movable mirror for reflecting light passing through the optical waveguide, and driving means for moving the movable mirror, the movable mirror being disposed so as to be inserted into the groove. In this case, as mentioned above, an optical switch constituted by the first optical circuit and actuator structure can be realized with a simple configuration.
Preferably, in this case, the movable mirror is attached to a cantilever supported on the planar waveguide; whereas the driving means comprises an electrode disposed on the planar waveguide, and means for generating an electrostatic force between the cantilever and the electrode. As a consequence, no current flow is necessary, whereby the power consumption can be reduced.
In still another aspect, the present invention provides an optical add/drop apparatus comprising the above-mentioned optical module. When the optical module has an optical switch and an optical variable attenuator, for example, the optical switch is constituted by the first optical circuit of the planar waveguide and the first actuator section of the actuator structure, whereas the optical variable attenuator is constituted by the second optical circuit of the planar waveguide and the second actuator section of the actuator structure, whereby the optical switch and optical variable attenuator can be made easily at a low cost as mentioned above.
In still another aspect, the present invention provides an optical transmission apparatus comprising the above-mentioned optical module. In this case, the optical switch of the optical module is constituted by the first optical circuit of the planar waveguide and the actuator structure, whereas the optical coupler of the optical module is constituted by the second optical circuit of the planar waveguide, whereby the optical switch and optical coupler can be made easily at a low cost as mentioned above. The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.